U.S. patent number 4,136,405 [Application Number 05/792,186] was granted by the patent office on 1979-01-30 for rotational offset knee prosthesis.
This patent grant is currently assigned to Zimmer U.S.A.. Invention is credited to John M. McDaniel, Dan L. Pastrick.
United States Patent |
4,136,405 |
Pastrick , et al. |
January 30, 1979 |
Rotational offset knee prosthesis
Abstract
A knee joint prosthesis comprises cooperating femoral and tibial
components and a coupling which is arranged to make a hinged
connection therebetween. Interdisposed hinge knuckles and a
cooperating pintle define a lateral-medial pivot axis that is
located posteriorly of the intersection between the intermedullary
femoral and tibial axes. A pair of transverse confronting plateaus
transmit vertical load forces between the elements of the
prosthesis. A proximal-distal axle and a cooperating tubular
bearing afford rotational motion, and this motion is limited by a
stop system, which system is also arranged to permit restricted
distraction.
Inventors: |
Pastrick; Dan L. (Warsaw,
IN), McDaniel; John M. (Warsaw, IN) |
Assignee: |
Zimmer U.S.A. (Warsaw,
IN)
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Family
ID: |
25156065 |
Appl.
No.: |
05/792,186 |
Filed: |
April 29, 1977 |
Current U.S.
Class: |
623/20.25 |
Current CPC
Class: |
A61F
2/384 (20130101) |
Current International
Class: |
A61F
2/38 (20060101); A61F 001/24 () |
Field of
Search: |
;3/1.911,1.91,1.9,22
;128/92C |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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|
2122390 |
|
Jan 1973 |
|
DE |
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2154338 |
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May 1973 |
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DE |
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2545821 |
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Apr 1976 |
|
DE |
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Primary Examiner: Frinks; Ronald L.
Attorney, Agent or Firm: Olson, Trexler, Wolters, Bushnell
& Fosse, Ltd.
Claims
The invention is claimed as follows:
1. A knee joint prosthesis comprising: a femoral component
including first fixation means defining a generally longitudinal
axis and first hinge knuckle means disposed posteriorly of said
longitudinal axis to cooperate in defining an offset,
lateral-medial pivot axis; a tibial component including second
fixation means, a first transverse plateau and a proximal-distal
extending tubular bearing; coupling means disposed generally
interjacent said femoral and tibial components and including second
hinge knuckle means cooperatively interdisposed with said first
hinge knuckle means to receive a hinge pintle, a generally
proximal-distal aligned pendent axle slidably rotatably received in
said tubular bearing and a second transverse plateau confronting
said first plateau to transmit vertical load forces therebetween; a
hinge pintle slidably and rotatably indwelling said first and
second hinge knuckle means; and stop means acting between said
first and second plateaus to restrict the arcuate degree of
rotation of said axle relative to said tubular bearing, said stop
means including bumper post means on one of said plateaus and a
pair of spaced notches on the other of said plateaus, said notches
being selectively and alternatively abuttable with said bumper post
means to define respective extremes of relative rotation about a
generally proximal-distal axis.
2. A knee joint prosthesis comprising: a femoral component
including first fixation means defining a generally longitudinal
axis and first hinge knuckle means disposed posteriorly of said
longitudinal axis to cooperate in defining an offset,
lateral-medial pivot axis; a tibial component including second
fixation means, a first transverse plateau and a proximal-distal
extending tubular bearing; coupling means disposed generally
interjacent said femoral and tibial components and including second
hinge knuckle means cooperatively interdisposed with said first
hinge knuckle means to receive a hinge pintle, a generally
proximal-distal aligned pendent axle slidably rotatably received in
said tubular bearing and a second transverse plateau confronting
said first plateau to transmit vertical load forces therebetween; a
hinge pintle slidably and rotatably indwelling said first and
second hinge knuckle means; and comprising spaced guide channel
means mounted on one of said plateaus, each of said guide channel
means including an upper and a confronting lower flange, said
flanges being spaced apart to admit therebetween and selectively
confine the other of said plateaus for limited proximal-distal
distraction of said plateaus through a predetermined arc of
relative movement thereof.
3. A knee joint prosthesis according to claim 2 wherein said guide
channel means are asymmetrically disposed for release of said
plateaus to free relative proximal-distal movement thereof adjacent
one terminus of said predetermined arc.
4. A knee joint prosthesis according to claim 2 which further
comprises bearing surface means acting between said other plateau
and confronting surfaces of said flanges.
5. A knee joint prosthesis according to claim 4 wherein said
plateaus include flat, confronting faces and which prosthesis
further comprises disk-like shock-absorbing and antifriction
bearing means disposed between said plateau faces.
Description
BACKGROUND OF THE INVENTION
This invention relates generally to orthopedic appliances, more
particularly to joint prostheses and especially to devices for the
surgical repair of the human knee.
Of the multitude of skeletal joints found in the human body, the
knee is generally regarded as being the most inherently unstable,
due in part to the complex of interrelated types of motion to which
the several knee elements are subjected during the normal acts of
walking, running, climbing stairs and the like. These motions
include relative sliding and rolling as well as rotation about both
horizontal and vertical axes; and in the past, a considerable
variety of mechanical approaches have been proposed in the attempt
to approximate, through an artificial joint, the natural action of
the human knee. Advanced conditions of disease or serious traumatic
injury of the knee joint further complicate surgical repair and
efforts to simulate the natural knee motion through use of a
prosthesis.
Under circumstances wherein the condyles of the knee are beyond
acceptable repair by means of surgical replacement of only the
articular surfaces thereof, it has been common practice heretofore
to attempt joint reconstruction by means of one or the other of two
general types of prostheses, viz. a first type which relies on a
mechanical hinge and the second which is characterized by a
ball-and-socket arrangement. The former type has as typical
objections the transmission of excessive torsional loads to the
fixation interface between the prosthesis and the leg bones and the
disposition of the transverse pivot axis in an unnatural location.
The latter type of device is difficult to install in proper
alignment during surgical implantation.
Accordingly, a general object of the present invention is to
provide a new and improved joint prosthesis for the replacement of
a seriously impaired human knee.
Another object of the invention is to provide a knee joint
prosthesis which combines the mechanical strength of a pintle hinge
with carefully limited rotational freedom.
Still another object of the invention is to provide a knee joint
prosthesis of the type described which situates the horizontal
pivot axis in a natural location posteriorly offset from the
tibial-femoral intersect.
A further object of the invention is to provide a knee joint
prosthesis of the type described which affords ease of alignment
and assembly during its surgical installation.
A yet further object of the invention is to provide a knee joint
prosthesis of the type described which incorporates a non-metallic
shock absorber and bearing element that can be easily replaced.
These and other objects and features of the invention will become
more apparent from a consideration of the following
descriptions.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention, both as to its construction and its mode of
operation, will be better understood by reference to the following
disclosure and drawings forming a part thereof, wherein:
FIG. 1 is a sagittal, partial sectional view taken from the medial
aspect and representing a human right knee that has been implanted
with a knee prosthesis constructed in compliance with the present
invention;
FIG. 2 is an anterior view of the installed prosthesis of FIG.
1;
FIG. 3 is a top plan view of the prosthesis of FIG. 1 with the
femoral components removed to show the rotational stop
arrangement;
FIG. 4 is a view similar to the showing of FIG. 3 but illustrating
a different relative rotational position of the parts, which
position allows free axial distraction of the components; and
FIG. 5 is an exploded perspective view of the illustrated
prosthesis.
DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENT
Referring now to the detail in drawings, specifically to FIGS. 1
and 2, the knee region of a human right leg is illustrated
generally by the reference numeral 10; and the joint of this knee
is shown to have been repaired by a total joint prosthesis 12 which
has been constructed and installed in compliance with the present
invention. The joint prosthesis 12 broadly comprises a femoral
component 14, a tibial component 16, and a coupling member 18; and
in order to provide the desired degree of mechanical strength,
these parts are fabricated from a metal alloy having proved
compatability with body tissues, such as the
cobalt-chromium-molybdenum compositions known in the medical arts
by the trade designation "Zimaloy". As will be described more fully
hereinafter, other parts of the prosthesis 12 are fashioned from
non-metallic materials, such as ultrahigh molecular weight
polyethylene and silicone rubber, in order to provide special
shock-absorbing and anti-friction properties and to minimize
metal-to-metal contact.
Structurally, the femoral component 14 includes a femoral
intermedullary stem 20, a basal member 22, a hinge knuckle
arrangement 24 and a patella plate member 26. The intermedullary
stem 20 has a generally longitudinal axis extending from the basal
member 22 to a tapering distal tip 28, as is best seen in FIG. 2.
In addition, the lateral and medial faces of the generally
rectangular stem 20 are grooved with proximally converging kerbs 30
to establish locking engagement in a quantity of bone cement 32
with which the stem 20 is secured in a bore 34 drilled axially of
femur 36. In order to promote fixation, the intermedullary stem 20
is slightly posteriorly inflexed at an intermediate point 38.
In order to achieve more nearly natural bending action in the
prosthesis 12, the hinge knuckle arrangement 24 is disposed
posteriorly of the longitudinal axis of the intermedullary stem 20,
as is best seen in FIG. 1. Turning to FIG. 5, the hinge knuckle
arrangement 24 of the femoral component 14 specifically includes a
pair of axially spaced, generally tubular, transversal hinge
knuckles 40, the knuckles 40 being fashioned with central bores 42
which are smoothly finished for slidably and rotatably receiving a
hinge pintle 44 in defining a horizontal pivot axis. Returning to
FIG. 1, the basal member 22 of the femoral component 14 is provided
with a transverse planar surface 46 which confronts the open space
between the hinge knuckles 40 for purposes which will be described
hereinafter; and the patella plate member 26 of the femoral
component 14 includes an angulated anterior groove 48 which is
slidably engaged by an artificial patella prosthesis 50, or by the
natural patella, in guiding relationship therewith. The latter
arrangement assures the desirable continuity of quadriceps tendon
52 and patellar ligament 54. When the patella prosthesis 50 is
employed, it is advantageously affixed in a cavity excavated
posteriorly of patella 56 by means of integral, wedge-shaped studs
58 and a suitable quantity of bone cement 60.
Continuing now with reference to FIGS. 1, 2 and 5, the tibial
component 16 is seen to include a tibial intermedullary stem 62, a
transverse plateau 64 and a central bore 66, bore 66 defining a
proximal-distal extending, tubular bearing for purposes of
affording rotation about a generally vertically disposed axis, as
is best seen in FIG. 1. The intermedullary stem 62 is intended to
be secured in the marrow channel of tibia 68 within an axial bore
70 drilled in the tibia and employing a suitable quantity of bone
cement 72. The stem 62 is tapered, narrowing generally in the
distal direction, and is provided with lateral and medial grooves
74 which promote secure fixation. In addition, a medial-lateral
flange 76 depends from transverse plateau 64 posteriorly of the
intermedullary stem 62 to reside in a trench 78 excavated in the
head of tibia 68, flange 76 being fixed therein by means of a
suitable quantity of bone cement. The flange 76 serves to secure
the tibial component 16 against torsional forces tending to loosen
the component from its fixated condition.
The coupling member 18 which is generally disposed interjacent the
femoral and tibial components 14 and 16 will now be described with
principal reference to FIG. 5; and as is seen in that illustration,
the member 18 includes a single hinge knuckle 80, a transverse
plateau 82 and a generally proximal-distal aligned, pendent axle or
stub shaft 84. The hinge knuckle 80 of coupling member 18 is sized
to be nested slidably between the hinge knuckles 40 of femoral
component 14, as is illustrated in FIG. 2, and to be rotatably
coupled therewith by means of the hinge pintle 44 dwelling in said
knuckles. To facilitate surgery, the hinge pintle 14 is arranged to
be inserted medially-laterally and for that purpose is fashioned
with a terminal flange or head 86 which fits within a conical
countersink in the end of the medial hinge knuckle 40. A snap ring
88 is intended to reside in a circumferential groove 90 adjacent
the lateral end of the hinge pintle 44 for abuttably engaging a
shoulder 92 provided in the lateral hinge knuckle 40, as is shown
in FIG. 2.
The plateau 82 of coupling member 18 confronts the plateau 64 of
tibial component 16 to transmit vertical load forces therebetween;
and in compliance with a feature of the present invention, a
bearing washer 94 is situated between the plateaus 64 and 82 for
purposes of absorbing shock and providing antifriction properties
between the two plateaus. Advantageously, the washer 94 is
fabricated from ultra-high molecular weight polyethylene or a
composite material based on such a resin.
In compliance with a further feature of the present invention, a
resilient stop is arranged to act between the coupling member 18
and the femoral component 14 for determining the extreme extension
condition of the knee prosthesis 12; and in the illustrated
embodiment, a resilient bumper block 96 is suitably mounted on the
coupling member 18 to face in the anterior direction as is shown in
FIG. 1. So disposed, the bumper block 96 confronts the transverse
surface 46 and engages that surface in the position of extreme
extension of the limb to avoid metal-to-metal contact and
resiliently arrest motion.
In accordance with another feature of the invention, a stop system
is arranged to act between the plateaus 64 and 82 so as to restrict
the degree of relative rotation between the axle 84 and the tubular
bearing 66. The stop arrangement provided for this purpose in the
illustrated embodiment will now be described with reference to
FIGS. 3-5 inclusive. There, the stop system includes a stop or
bumper post 98 upstanding from the tibial plateau 64 and both a
lateral notch 100 and a medial notch 102 fashioned in the anterior
edge of coupling member plateau 82. In addition, a semi-cylindrical
guard element 104 is removably mounted on post 98, the element 104
being fabricated from a suitable resinous plastics material in
order to eliminate metal-to-metal contact between the plateau 82
and the post 98. Moreover, the element 104 is fabricated with
confronting, anterior tongues 106, as shown in FIG. 2, which snap
fit into cooperating notches 108 formed in the sides of post 98.
The washer 94 includes a circular cut-out to accomodate post 98 and
guard element 104.
It will be appreciated that the axle 84 is not only rotatable
relative to the tubular bearing 66 but axially slidable with
respect thereto, and it will be further appreciated that this
proximal-distal freedom is desirably restricted upon implantation
of the prosthesis 12. Accordingly, it is in accord with a still
further feature of the invention to provide an appropriate system
of limiting this longitudinal freedom. Specifically, and with
continued reference to FIGS. 3-5 inclusive, a pair of spaced guide
channel elements, medial guide channel element 110 and lateral
guide channel element 112, are included to extend from the tibial
plateau 64 in the proximal direction. Each of the guide channel
elements 110 and 112 comprises an upper flange 114 and a
confronting lower flange 116, the flange 114 and 116 being
vertically spaced apart to admit therebetween and selectively
confine the coupling member plateau 82 for limited proximal-distal
distraction of the plateaus through the predetermined arc of
relative movement thereof. The two extremes of this arc of movement
are defined first, by the abutment of notch 100 and the
semi-cylindrical guard element 104, as is shown in FIG. 3, and
second, by the corresponding abutment of notch 102 and guard
element 104 in the opposite position of relative rotation of the
parts. The confinement of coupling member plateau 82 by the guide
channel elements 110 and 112 is additionally shown in FIG. 2.
Furthermore, undesirable metal-to-metal contact between the plateau
82 and the upper flanges 114 as avoided by installing a pair of
resinous plastic wear and bumper plates 118 on the proximal surface
of coupling member plateau 82. These plastic plates 118 desirably
take the shape of the segment of an arc corresponding in
approximate angular extent to the amount of limited relative
rotational movement that is permitted between the coupling member
18 and the tibial component 16. As will be appreciated, the washer
94 is selected to take a sufficient thickness to prevent
metal-to-metal contact between the lower flanges 116 and the distal
or undersurface of coupling member plateau 82.
The prosthesis 12 is advantageously arranged, in accordance with a
still further feature of the invention, for ease of alignment of
the respective components during surgical installation. For this
purpose, the guide channel elements 110 and 112 are asymmetrically
arcuately arranged, as shown in FIGS. 3 and 4. Thus, in the absence
of the post guard element 104, as is suggested in broken outline in
FIG. 4, the coupling member plateau 82 may be rotated relative to
the tibial plateau 64 so that the wear plates 118, and the
underlying portions of plateau 82, escape from confinement between
the flanges 114 and 116 of both of the guide channel elements. In
this latter position of relative rotation of the coupling member
and the tibial component, these parts are freed to relative
proximal-distal movement, either for assembly of the prosthesis
approaching the end of surgery, or for surgical replacement of
either the bearing washer 94 and/or the entire coupling member 18
upon indication of the necessity for such activity. As will be
appreciated, when the prosthesis is assembled in its configuration
of use, the act of fitting the post guard element 104 on post 98
locks the plateau 82 against sufficient rotation to escape
confinement between the guide channel elements 110 and 112.
Procedural variants for surgically implanting the prosthesis 12 in
repair of a diseased or traumatized human knee will be evident to
surgeons skilled in the orthopedic arts.
The drawings and the foregoing descriptions are not intended to
represent the only form of the invention in regard to the details
of its construction and manner of operation. Changes in form and in
the proportion of parts, as well as the substitution of
equivalents, are contemplated, as circumstances may suggest or
render expedient; and although specific terms have been employed,
they are intended in a generic and descriptive sense only and not
for the purposes of limitation, the scope of the invention being
delineated in the following claims.
* * * * *